This Friday an unconventional walking tour will lead participants through a series of publically accessible -- if rarely seen -- parts of Chicago’s Loop: its lobbies, Pedway passages, shortcuts, corridors, and other indoor interstitial spaces.

In 1991 most Chicagoans knew nothing about the freight tunnels that ran underneath the city. That would change after a contractor sank wooden pilings into the river at the Kinzie Street Bridge and caused crack in one of the tunnel walls.

Skyscraper!We're so used to hearing the word, we don't really think about it. Today we have airplanes. We've flown to the moon. Scraping the sky doesn't seem like such a big deal.But go back to this date in 1884.